A contact-type IC card internally having a semiconductor integrated circuit having the functions of a CPU, a memory, and the like and having, on the surface of the card, a contact terminal with the semiconductor integrated circuit is being widespread in the fields of finance and the like.
In the contact-type IC card, writing, erasure, and reading of data to/from the memory by the CPU or the like are controlled and, by having a cipher processing function and the like, high security performance of the contact-type IC card is realized. In a CPU or the like realizing such a function, device withstand voltage is decreasing due to refinement of the semiconductor process of these days, and the withstand voltage of the power supply voltage supplied to the CPU is suppressed. Consequently, the power supply voltage is commonly supplied to the CPU and the like via a regulator circuit which suppresses the voltage level from the power supply voltage terminal.
On the other hand, a noncontact-type IC card having no power supply such as a battery, generating a power supply voltage for operating internal circuits from electromagnetic waves received by an antenna, and operating on the generated voltage is being actively used in the fields of traffic and the like. A noncontact-type IC card receives data obtained by modulating electromagnetic waves and sent from a reader/writer (interrogator), according to data obtained by processing the received data, modulates the electromagnetic waves received by the antenna by fluctuating the load between the antenna terminals, and transmits the data to the reader/writer (interrogator).
Like the contact-type IC card, also in the noncontact-type IC card, a CPU, a memory, and the like are mounted in order to realize the above-described function. Consequently, a power supply voltage which is suppressed so as not to exceed a withstand voltage of an element as a component of the CPU is supplied to the CPU and the like.
In a dual-way IC card having both the function of a contact-type IC card and the function of a noncontact-type IC card, according to the operation state of the IC card, a power supply voltage which is supplied from a power supply voltage terminal provided as a contact terminal via a regulator circuit or a power supply voltage generated from electromagnetic waves received by an antenna is selectively supplied to an internal circuit such as a CPU mounted internally.
To prevent short-circuit of an input voltage supply which may occur in the case where a plurality of power supply input units are provided and a supplied power is switched and used and to prevent short-circuit between a power supply terminal and a ground terminal which is caused by contact of metal or the like in a noncontact operation, it is necessary to isolate a power supply input other than the selected power supply.
For the purpose, there is a technique of interrupting an input from a power supply voltage terminal in the case of providing a power supply switch circuit between the power supply voltage terminal and an internal power supply line and performing operation on power generated from electromagnetic waves received by an antenna (refer to patent document 1).
In the case of configuring the power supply switch circuit described in the patent document 1 by a PMOS transistor, a current path is generated between the power supply voltage terminal and the internal power supply line via a parasitic diode formed between a bulk terminal of the PMOS transistor and the source terminal. Consequently, the internal power supply line cannot be completely interrupted from the power supply voltage terminal.
There is consequently a technique of completely interrupting the internal power supply line from the power supply voltage terminal without generating the current path via the parasitic diode by configuring the power supply switch circuit by two PMOS transistors which are coupled in series (refer to patent document 2).    Patent Document 1: Japanese Unexamined Patent Publication No. 2000-113148    Patent Document 2: Japanese Unexamined Patent Publication No. 2004-78898